<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
  
  .wrapper{
    display: grid;
    grid-template-columns: 30% 70%;
    grid-template-rows: 100px 600px 50px;
  }
  .container{
    display: grid;
    grid-template-columns: 30% 70%;
    grid-template-rows: 100%;
  }
  .footer,.header,.container{
    grid-column: 1 / 4;
    background: lightgreen;
    text-align: center;
    line-height: 50px;
  }
  .nav{
    grid-column: 1 / 2;
    grid-row: 1 / 2;
    background: sandybrown;
  }
  .cont{
    grid-column: 2 / 4;
    grid-row: 1 / 2;
    background: salmon;
  }
  </style>
</head>
<body>
  <div class="wrapper">
    <div class="header">header</div>
    <div class="container">
      <div class="nav">nav</div>
      <div class="cont">cont</div>
    </div>
    <div class="footer">footer</div>
  </div>
</body>
</html>